@monstermann/fn/dist/array/filter.js

A utility library for TypeScript.

import { addRange, createRange, hasRange, spliceRange } from "./internals/range.js";
import { dfdlT } from "@monstermann/dfdl";
import { cloneArray } from "@monstermann/remmi";

//#region src/array/filter.ts
/**
* `filter(target, by)`
*
* Filters elements from `target` array based on the predicate function `by`.
*
* ```ts
* filter([1, 2, 3, 4], (x) => x > 2); // [3, 4]
* ```
*
* ```ts
* pipe(
*     [1, 2, 3, 4],
*     filter((x) => x > 2),
* ); // [3, 4]
* ```
*/
const filter = dfdlT((target, by) => {
	const range = createRange();
	for (let i = 0; i < target.length; i++) if (!by(target[i], i, target)) addRange(range, i);
	if (hasRange(range)) {
		const result = cloneArray(target);
		spliceRange(result, range);
		return result;
	}
	return target;
}, 2);

//#endregion
export { filter };